<template>
	<view class="easy-loadimage" :id="uid">
		<image
			class="origin-img"
			:src="imageSrc"
			:mode="mode"
			v-if="loadImg && !isLoadError"
			v-show="showImg"
			:class="{
				'no-transition': !openTransition,
				'show-transition': showTransition && openTransition,
			}"
			@load="handleImgLoad"
			@error="handleImgError"
		>
		</image>
		<view class="loadfail-img" v-else-if="isLoadError"></view>
		<!-- <view :class="['loading-img','spin-circle',loadingMode]" v-show="!showImg&&!isLoadError"></view> -->
	</view>
</template>
<script>
import { throttle } from "@/utils/validate.js";

// 生成全局唯一id
function generateUUID() {
	return "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(/[xy]/g, function (c) {
		let r = (Math.random() * 16) | 0,
			v = c == "x" ? r : (r & 0x3) | 0x8;
		return v.toString(16);
	});
}
export default {
	name: "easy-loadimage",
	props: {
		imageSrc: {
			type: String,
		},
		mode: {
			type: String,
			default: "aspectFit",
		},
		loadingMode: {
			type: String,
			default: "looming-gray",
		},
		openTransition: {
			type: Boolean,
			default: true,
		},
		viewHeight: {
			type: Number,
			default() {
				return uni.getSystemInfoSync().windowHeight;
			},
		},
	},
	data() {
		const that = this;
		return {
			// uid:'',
			uid: "uid-" + generateUUID(),
			loadImg: false,
			showImg: false,
			isLoadError: false,
			showTransition: false,
			scrollFn: throttle(function () {
				// 加载img时才执行滚动监听判断是否可加载
				if (that.loadImg || that.isLoadError) return;
				const id = that.uid;
				const query = uni.createSelectorQuery().in(that);
				query
					.select("#" + id)
					.boundingClientRect((data) => {
						if (!data) return;
						if (data.top - that.viewHeight < 0) {
							that.loadImg = !!that.imageSrc;
							that.isLoadError = !that.loadImg;
						}
					})
					.exec();
			}, 200),
		};
	},
	methods: {
		init() {
			this.$nextTick(this.onScroll);
		},
		handleImgLoad(e) {
			this.showImg = true;
			this.showTransition = true;
		},
		handleImgError(e) {
			this.isLoadError = true;
		},
		onScroll() {
			this.scrollFn();
		},
	},
	mounted() {
		this.init();
		uni.$on("scroll", this.scrollFn);
		this.onScroll();
	},
	beforeDestroy() {
		uni.$off("scroll", this.scrollFn);
	},
};
</script>

<style scoped>
/* 官方优化图片tips */
image {
	will-change: transform;
}
/* 渐变过渡效果处理 */
image.origin-img {
	width: 100%;
	height: 100%;
	opacity: 0.3;
	/* min-height: 360rpx; */
}
image.origin-img.show-transition {
	transition: opacity 0.5s;
	opacity: 1;
}
image.origin-img.no-transition {
	opacity: 1;
}
.easy-loadimage {
	overflow: hidden;
	/* border: 1rpx solid #D9DFE7; */
}
/* 加载失败、加载中的占位图样式控制 */
.loadfail-img {
	height: 100%;
	background: url("@/static/easy-loadimage/loadfail.png") no-repeat center;
	background-size: 50%;
}
.loading-img {
	height: 100%;
}
/* 转圈 */
.spin-circle {
	background: url("@/static/easy-loadimage/loading.gif") no-repeat center;
	background-size: 100rpx;
}
/* 动态灰色若隐若现 */
.looming-gray {
	animation: looming-gray 1s infinite linear;
	background-color: #e3e3e3;
}
@keyframes looming-gray {
	0% {
		background-color: #e3e3e3aa;
	}
	50% {
		background-color: #e3e3e3;
	}
	100% {
		background-color: #e3e3e3aa;
	}
}
/* 骨架屏1 */
.skeleton-1 {
	background-color: #e3e3e3;
	background-image: linear-gradient(
		100deg,
		rgba(255, 255, 255, 0),
		rgba(255, 255, 255, 0.2) 50%,
		rgba(255, 255, 255, 0) 80%
	);
	background-size: 100rpx 100%;
	background-repeat: repeat-y;
	background-position: 0 0;
	animation: skeleton-1 0.6s infinite;
}
@keyframes skeleton-1 {
	to {
		background-position: 200% 0;
	}
}
/* 骨架屏2 */
.skeleton-2 {
	background-image: linear-gradient(
		-90deg,
		#fefefe 0%,
		#e6e6e6 50%,
		#fefefe 100%
	);
	background-size: 400% 400%;
	background-position: 0 0;
	animation: skeleton-2 1.2s ease-in-out infinite;
}
@keyframes skeleton-2 {
	to {
		background-position: -135% 0;
	}
}
</style>
